Hi Paul,
I have no problem with your statement, in fact, I would be surprised if otherwise.
HOWEVER, peel strength does not correlate with SJ fatigue reliability.
Since that was what was asked by Mordechai, I stand by me statement.
Werner
-----Original Message-----
From: Paul Edwards <[log in to unmask]>
To: TechNet E-Mail Forum <[log in to unmask]>; Werner Engelmaier <[log in to unmask]>
Sent: Tue, May 4, 2010 5:24 pm
Subject: RE: [TN] Minimum Side Joint Length
Werner,
I beg to differ...
When I did peel tests with TABed parts I found a +30% increase in peel strength when I had side fillets verses not having any...
Without side fillets you end up peeling through the lap joint surface interface...
With side fillets, your peel forces must propagate through bulk solder and not only just through the lap joint interface....
Paul
Paul Edwards
Surface Art Engineering
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Tuesday, May 04, 2010 5:08 AM
To: [log in to unmask]
Subject: Re: [TN] Minimum Side Joint Length
Hi Mordechai,
I would not worry too much about side fillets--the heel fillets are much more important.
What should be your real concern about the reliability of your TSOPs SJs is whether your TSOP leadframe is made of Alloy 42 instead of copper. That is where your reliability concern needs to be because of the large CTE-mismatch with FR-4.
Werner
-----Original Message-----
From: Mordechai Kirshenbaum <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, May 4, 2010 7:43 am
Subject: [TN] Minimum Side Joint Length
We have to assemble TSOP packages on SSOP foot print PCB. (The TSOP
package width is 40 mils shorter than the SSOP package width).
We found that the theoretical ( calculated) side joint length (D) will be in
some
instances less than the minimum acceptable side joint (as by IPC-A-610,
#8.2.5.4). (The available pad length on the PCB under the component lead is
less than the foot length).
It may be even worse if we have a slight solder defect, or if the component is
placed several mils off side.
What is the reliability impact?
Do you know about accelerated reliability tests or field data that show the
correlation between the failure rate and the side joint length?
Thankfully,
Mordechai Kirshenbaum
QA Team Manager
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